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>6.9. Disks without filesystems</A
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><P
>Not all disks or partitions are used as filesystems.
	A swap partition, for example, will not have a filesystem on it.
	Many floppies are used in a tape-drive emulating fashion, so that a
	<B
CLASS="COMMAND"
>tar</B
> (tape archive) or other file is written 
	directly on the raw disk, without a filesystem.  Linux boot floppies
	don't
	contain a filesystem, only the raw kernel.</P
><P
>Avoiding a filesystem has the advantage of making more of
	the disk usable, since a filesystem always has some bookkeeping
	overhead.  It also makes the disks more easily compatible with other
	systems: for example, the <B
CLASS="COMMAND"
>tar</B
> file format is the
	same on all systems, while filesystems are different on most
	systems.  You will quickly get used to disks without filesystems if
	you need them.  Bootable Linux floppies
	also do not necessarily have a filesystem, although they may.</P
><P
>One reason to use raw disks is to make image copies of them.
	For instance, if the disk contains a partially damaged filesystem,
	it is a good idea to make an exact copy of it before trying to fix
	it, since then you can start again if your fixing breaks things even
	more.  One way to do this is to use <B
CLASS="COMMAND"
>dd</B
>:

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>	<TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>dd if=/dev/fd0H1440 
	of=floppy-image</B
></TT
>
	<TT
CLASS="COMPUTEROUTPUT"
>2880+0 records in
	2880+0 records out</TT
>
	<TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>dd if=floppy-image 
	of=/dev/fd0H1440</B
></TT
>
	<TT
CLASS="COMPUTEROUTPUT"
>2880+0 records in
	2880+0 records out</TT
>
	<TT
CLASS="PROMPT"
>$</TT
>
	</PRE
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>

	The first <B
CLASS="COMMAND"
>dd</B
> makes an exact image of the floppy
	to the file <TT
CLASS="FILENAME"
>floppy-image</TT
>, the second one writes
	the image to the floppy.  (The user has presumably switched the
	floppy before the second command.	Otherwise the
	command pair is of doubtful usefulness.)</P
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